A resistance heating element utilizing a helical wire coil is made with a linear frame configuration and provided with relieved or notched areas permitting the frame to be reshaped from its linear configuration to a circular or other arcuate shape for mounting and use in a heating and/or drying appliance. More particularly, one embodiment of the description applies the reformed frame to a circular air duct housing component for a dryer.
In a basic embodiment of this disclosure, a formable helical wire heating coil assembly is adapted for attachment to a generally circular housing component, the assembly comprising an elongate sheet metal frame that has an angular cross sectional shape including a first leg and a second leg, the frame having spaced along its length and formed integrally therewith a linear array of open notches in the first leg, the notches having spaced edges that extend from the second leg to the free edge of the first leg. The frame is formable from its linear configuration in the plane of the first leg to at least partially close the notches and permitting the frame to assume a circular shape. In another embodiment, the frame includes an integrally formed linear array of clips for mounting insulating stand-offs in a spaced arrangement along the length of the frame. In a further embodiment, the frame includes an integrally formed linear array of attachment tabs spaced along the length of the frame for attaching the frame to the housing component.
In a method related to making the apparatus described above, a helical wire coil assembly adapted for attachment to a generally circular housing component is made by the method comprising the steps of: (1) for wing a straight elongate sheet metal frame having an angular cross sectional shape including a first leg and a second leg; (2) providing the frame along its length with an integrally formed linear array of open notches in the first leg which notches have spaced edges that extend from the second leg to the free edge of the first leg; and, (3) forming the frame in the plane of the first leg to at least partially close the notches and permit the frame to assume an arcuate shape. The method may also include the step of providing the frame along its length with a linear array of attachment tabs for connection to the housing component. The method may also include the step of providing the frame along its length with an integrally formed linear array of clips for attachment of insulting stand-offs.
In another embodiment of this disclosure, a formable helical wire heating coil assembly is adapted to be attached to a generally circular housing component with the assembly comprising an elongate sheet metal frame that has an angular cross sectional shape including a first leg and a second leg, the frame having spaced along its length and formed integrally therewith a linear array of open notches in the horizontal leg, the notches having spaced edges that extend from the second leg to the free edge of the first leg, whereby the frame is formable in the plane of the first leg to at least partially close the notches and cause the frame to assume a circular shape. Preferably, the notches are formed in a V-shape with the notch edges divergent toward the free edge of the first leg. The notches are preferably formed such that the notch edges abut in the smallest diameter form of the frame.
In a further embodiment of this disclosure, the circular array of attachment slots is formed in the planar face of the housing component and the array of attachment tabs is provided with a spacing that corresponds to the spacing of the attachment slots. When the frame is formed to a circular shape, the tabs are received in the slots. Preferably, the tabs are locked in the slots and, more preferably, the tabs are locked by twisting.
In a further embodiment, the clips extend from the free edge of the second leg and in the plane thereof. Preferably, the clips have bifurcated free ends that are defined by generally parallel clip legs, and the stand-offs have a grooved body to receive the clip legs. A helical wire heating coil is attached to and supported by the stand-offs.
In another embodiment of this disclosure, a method of making a helical wire coil assembly is adapted for attachment to a generally circular housing component and includes the steps of forming a straight elongate sheet metal frame having an angular cross sectional shape that includes a first leg and a second leg; providing the frame along its length with integrally formed linear arrays of: clips for insulating stand-offs; attachment tabs for the housing component; and, open notches in the first leg having spaced edges extending from the second leg to the free edge of the first leg and forming the frame in the plane of the first leg to at least partially close the notches and to assume an arcuate shape. Preferably, the method includes the steps of forming the notches in a V-shape with side edges that diverge toward the free edge of the first leg, and forming the frame in the plane of the first leg to close the notches and to assume the arcuate shape. The arcuate shape is preferably circular. In a further embodiment, the step of forming the frame includes causing the edges of the notches to abut.
In a further embodiment of the method, steps are provided for: forming a circular array of attachment slots in a planar face of the housing component; providing the array of attachment tabs with a spacing that corresponds to the spacing of the attachment slots; and, forming the frame to a circular shape in which the tabs are received in the slots. The step preferably includes locking the tabs in the slots. More preferably, the locking step comprises twisting the tabs.
The modified embodiment of the disclosed method may include the steps of: forming the clips to extend from the free edge of the second leg and in the plane thereof; providing the clips with a bifurcated free end defined by generally parallel clip legs; and, providing the insulating stand-offs with a grooved body positioned to receive the clip legs. This method preferably includes the step of attaching a helical wire heating coil to the stand-offs. The method may also include the step of squeezing the clip legs toward each other to lock the stand-off in the clip.
In a further embodiment, the method includes the steps of: forming the notches in the straight frame to provide the notches with generally parallel spaced edges; and, forming the frame to the arcuate shape and causing the notches to close such that the outermost ends of the notch edges converge at the free edge of the first leg. The arcuate shape to which the frame is formed is preferably circular. Further, the step of forming the frame preferably includes causing the ends of the notch edges at the free edge of the frame to abut.
In a presently preferred method of this application for making a helical wire coil assembly adapted for attachment to a generally circular assembly housing component, the method includes the steps of: forming an elongate linear sheet metal frame having an angular cross-sectional shape including a first leg and a second leg; providing the frame along its length with integrally formed linear arrays of clips for insulating stand-offs and forming the clips to extend from the free edge of the second leg and in the plane thereof; attachment tabs in the first leg for the housing component and forming the tabs to extend generally perpendicular to the first leg and generally parallel to the clips; and, open notches in the first leg having a V-shape defined by spaced edges extending and diverging from the second leg to the free edge of the first leg; and, forming the frame in the plane of the first leg to close the notches and provide the assembly with a generally circular shape.
This disclosure also includes a method of packaging for shipment and use a helical wire heating coil assembly that, in use, is generally circular, the method comprising the steps of: forming a straight elongate sheet metal frame having an angular cross sectional shape that defines a first leg and a second leg; forming the first leg of the frame along its length with an integral linear array of open notches that extend from the second leg to the free edge of the first leg; providing a packaging and shipping container having a plurality of adjacent parallel enclosures sized to receive the straight frame; and, upon removal from the container, forming the frame in the plane of the first leg to at least partially close the notches to provide the circular shape. The method may also include the step of forming along the length of the frame integral linear arrays of clips for insulating stand-offs and attachment tabs for the housing component. The method also includes the step of attaching a helical wire heating coil to the stand-offs.